Methods for manufacturing armored cables



July 5, 1966 w. E. BOWERS 3,259,675

METHODS FOR MANUFACTURING ARMORED GABLES Original Filed Dec. 29, 1960W////0/77 f. Bowers J9 INVENTOR W Maw ATTORNEY United States PatentOriginal application Dec. 29, 1960, Ser. No. 79,390.-

Divided and this application June 18, 1963, Ser. No. 288,761

I 8 Claims. (Cl. 264-103) This application is a divisional applicationof my patent application Serial No. 79,390, filed December 29, 1960, andnow abandoned, for Armored Cables and Methods for Manufacturing ArmoredCables.

This invention relates to a method for manufacturing load-bearing,multiconductor, electrical cables. More particularly, the cablesconsidered are of the type employed in the logging of boreholes drilledinto earth formations.

In the performance of well logging and other similar subsurfaceoperations, instruments are lowered into boreholes, often to depths oftwenty thousand feet or more, by means of a cable which is spooled upona mobile field unit. The physical conditions to which such cables aresubjected by the borehole environment may be extremely harsh. Forexample, the cable is subject to severe abrasion by contact with theborehole Wall; temperatures of 350 Fahrenheit or more are not uncommonin very deep boreholes; the hydrostatic pressure of the drilling fluidwithin the borehole may reach ten thousand pounds per square inch ineven a comparatively shallow well; the fluids within the borehole areoften extremely saline; and the cable may be subjected to chemicaldegradation by oil, gas or other chemicals. Under such conditions, awell logging cable must perform satisfactorily the functions of: (l) awire rope having suflicient strength to support its own weight and theweight of the borehole instruments plus an additional margin of strengthto provide for emergency tensions and a reasonable safety factor; (2) amulticonductor transmission line to conduct electrical power and signalsbetween the borehole instruments and the surface equipment withoutexcessive electrical leakage or signal attenuation; and (3) a depthmeasuring line to locate the borehole instruments accurately withrespect to a surface datum. Moreover, to satisfy the requirements ofmobility and length, the cables must be of relatively small diameter andlight weight.

The above requirements have led to a general form of construction inwell logging cables which comprises at least two concentric layers ofload-bearing, metallic armor strands helically wound in oppositedirections about a core which contains a plurality of insulated,electrical conductors. The invention relates specifically to a new andimproved core in such multiconductor Well logging cables and to a methodof constructing the same; and an exemplary seven-conductor core will beconsidered herein for purposes of explanation. However, beforeconsidering the invention, a discussion of the cable art will beprovided so that the invention may be more fully understood in itsspecific aspects.

A typical seven-conductor cable core may comprise a central insulatedelectrical conductor arranged substantially coextensive with thelongitudinal axis of the core and six outer insulated electricalconductors helically wound about, and in direct contact with, thecentral insulated conductor. The insulation for the conductors mayconsist, for example, of individual tubular sheaths of a rubber compoundextruded about each of the conductors. In order to make the corerelatively compact, the diameter of the insulating sheaths and the layangles of the outer insulated conductors are selected so that adja-3,259,675 Patented July 5, 1966 cent outer conductors are in directcontact with one another. Cotton fillers are placed in the externalinterstices between adjacent outer conductors to give the core agenerally cylindrical form. This core assembly of insulated conductorsand fillers is enclosed within a tubular sheath, which may consist, forexample, of braided nylon strands. The sheath serves to protect theconductor insulation from being damaged by the inner layer of armorstrands. Alternatively, in place of the braided sheath a layer of tapemay be wrapped about the assembly.

Because of the extreme length and close proximity of the conductors in awell logging cable, electrical shielding must be utilized to reduce theeffects of capacitive coupling between conductors. For this purpose, theouter surface of the insulating sheath on each conductor is coated witha thin, electrically semiconductive film and the cotton fillers andnylon braid (or tape) are impregnated With an electricallysemiconductive compound. These steps are generally performed beforeassembly of the core by dipping the individual components in asemiconductive solution and then drying them to leave a semiconductiveresidue.

Thus, in the finished cable, each insulated conductor is surrounded by asemiconductive film which is electrically connected to the armor strandsthrough contact with the impregnated fillers or braids (or tape); andthe armor strands are normally maintained at electrical ground potentialthrough contact with the drilling fluid within the borehole or throughan electrical ground connection at the surface.

While cables with the above-described type of core are widely employedin the well logging industry, they have not been found entirelysatisfactory. Among their disadvantages are the following:

First, they are difficult to fabricate. When such cables are placed intension, the helically wound armor strands exert upon the coreassembly apressure which may approach, for example, five thousand pounds persquare inch for a cable tensionof only several thousand pounds. In orderto prevent the core assembly from being damaged by this pressure, it isnecessary that the armor strands lie close together to substantiallycover the core assembly. Such full and uniform armor coverage requiresthat the diameter of the core assembly be maintained within extremelyclose limits of accuracy, and such control is difiicult to achieve withthe type of built-up construction presently utilized.

Second, the length stability of the cables is poor. In order to measureaccurately the depth of borehole instruments, it is important thatchanges in the length of a given section of well logging cable bedeterminable. Changes in cable length resulting from elasticdeformation, which is a change in length with tension, or thermaldeformation, which is a change in length with temperature, may bedetermined with reasonable accuracy during well legging operations bymeasuring the cable tension and the borehole temperature and computingthe true length from previously derived charts. However, if anirreversible deformation takes place, the cable length cannot bedetermined without actually remeasuring the cable by comparison with alength standard. The term length stability, as used herein, is intendedto denote the property of a cable to resist such irreversibledeformations. It has been found that, as well logging cables of theabove described type are used, irreversible deformation does take place,particularly during the early periods of use. This results primarilyfrom the presence in the fillers and between the conductors and fillersof numerous void spaces, which permit the core to compact under pressureby the borehole fluid and the armor strands. Thus, the core diameterbecomes permanently smaller with a corresponding increase in cablelength. Such cables must be remeasured frequently, at least during theearly stages of use when most of the elongation occurs; or,alternatively, a method of treatment known as hot prestressing may beused to induce most of the compaction before the cable is used in thefield. This method is described in copending application Serial No.570,780, entitled Methods for Processing Cables, filed by AndreBlanchard On March 12, 1956. While this method affords a partialsolution to the length stability problem, alterations of the lay anglesof the conductors and armor strands resulting from cable elongation maylead to strains in particular portions of the cable or to otherundesirable effects. Hence, reduction of core compaction would be apreferred solution.

Third, the maximum operating temperature of the cables is limited by thephysical properties of the conductor insulation and the braid (orvtape)materials. As is well known, rubber materials are available in a vastvariety of compounds which may be varied to satisfy differingrequirements of hardness, temperature properties, electrical properties,resilience, oil and gas resistance, heat resistance, etc. However,particular properties often can be obtained only at the expense ofothers; hence, those rubber compounds which have the electricalproperties required to properly insulate the conductors do not have thephysical properties required to withstand the pressure of the armorstrands at the temperatures encountered in borehole use, One of thefunctions of the braided sheath (or tape) about the exterior of the coreassembly is to assist in containing the presently utilized rubbercompound and prevent it from extruding between the armor strands whenthe cable is hot and under tension. However, even these'materials arenot adequate to confine the rubber compounds at temperatures much higherthan 350 Fahrenheit.

Fourth, the cables are not highly resistant to the chemical effects ofoil or gas. The conductor insulation is particularly susceptible todegradation by oil or gas, due primarily to the above describednecessity of sacrificing some properties in order to secure otherdesired properties.

A-nd fifth, the electrical transmission characteristics of the cablesare not entirely satisfactory. This is also due, at least in part, tothe above described necessity for compromise in the selection ofmaterials for conductor insulation. For example, the insulationresistance of the compounds usable with the present form of constructiontends to decrease substantially with increase in temperature. Moreover,these compounds have a relatively high dielectric constant, whichresults in a relatively high capacitance to ground for each individualconductor. Further, the previously described method of electricalshielding to reduce the effects of capacitive coupling betweenconductors is not entirely effective. Perfect shielding would exist ifall parts of each conductive film around the individual conductors hadzero resistance to electrical ground. This condition is achieved to apractical degree for those portions of each film which are in directcontact with'the braid or fillers since current flow to electricalground is through a large cross section for a very short length.However, as isevident from the previously described structuralconfiguration of the core, less than half of the film around eachinsulated conductor is in such direct contact, and the remainingportions of the films may have a relatively high resistance to groundsince current must flow along the film for a relatively great length.The central conductor in particular is poorly shielded since itsboundary film has no direct contact with the fillers or braid.Additional resistance is introduced by breaks and discontinuities in thefilms resulting from inherent limitations in the process for applyingthe films or from subsequent strains or fiexures.

Accordingly it is an object of the invention to provide a new andimproved method of fabricating a load-bearing, multiconductor,electrical, well logging cable.

This and other objects are attained, in accordance with the invention,by providing an armored well logging cable with a core that improves thecharacteristics of the cable with respect to the above describeddeficiencies of the prior art. The core comprises a plurality ofelectrical conductors individually encased within tubular sheaths ofdielectric material, arranged in spaced-apart relationship, and embeddedwithin a generally cylindrical matrix comprising a hard, semiconductiveelastomer. The exemplary seven-conductor core described hereinincorporates an arrangement of conductors wherein a central insulatedconductor is substantially coextensive with the central axis of the coreand six outer insulated conductors arearranged helically in spaced-apartrelationship about the central axis and away from the central insulatedconductor.

In accordance with the method aspect of the invention, a new andimproved method of fabricating a well logging cable with a core of thetype described above is provided. For example, to fabricate an exemplarysevenconductor cable as described herein, tubular sheaths of dielectricmaterial are extruded about each of the conductors. The centralinsulated conductor is processed through another extruding machine to becovered with an uncured layer of the semiconductive matrix material. Theouter insulated conductors are wound in spacedapart relationship aboutthis inner layer of uncured matrix material and under sufficient tensionto partially embed them in its surface. This assembly is processedthrough a further extruding machine tobe covered with an uncured outerlayer of the matrix material, thus completing the core assembly. Thematrix material may then be cured and the layers of armor strands woundconcentrically about its outer surface; or, alternatively, the innerlayer of armor strands may be wound before the matrix material iscompletely cured and under sufiicient tension to partially embed thestrands into its surface.

The invention may best be understood, and further objects and advantageswill become apparent, from the following detailed description, taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a view in perspective of an armored, Well logging cableconstructed in accordance with the invention with successive componentsbroken away to show the details of the cable construction;

FIG. 2 is a view in cross section of the cable shown in FIG. 1; and

FIG. 3 is a schematic illustration of apparatus for carrying out themethod aspect of the invention.

The typical embodiment of the invention shown in FIGS. 1 and 2 comprisesa seven-conductor core 14 surrounded by two concentric layers ofload-bearing armor strands 10 and 12. The inner layer of armor strands12 comprises a plurality of metallic strands 13 wound with a right handlay about the core 14; and the outer layer of armor strands 10 similarlycomprises a plurality of metallic strands 11 wound with a left hand layabout the inner layer 12. The number, size and pitch of the strands 11and 13 are chosen so that the inner layer 12 substantially covers thecore 14 and the outer layer 10 substantially covers the inner layer 12.The armor strands perform the load-bearing functions of the cable andfurther serve to protect the core 14 from physical abuse and damage.Well logging cables employing concentric layers of armor strands, suchas 10 and 12, are well known in the art and further disclosure ofparticular materials, number and size of strands, or pitch angles istherefore considered unnecessary.

The core 14 comprises a central insulated conductor 21 arrangedsubstantially coextensive with the central axis of the cable, six outerinsulated conductors 17 wound with a left hand lay in spaced-apartrelationship about the central axis and away from the central insulatedconductor 21, and a monolithic matrix 15 having a generally cylindricalouter boundary and encasing all of the conductors and filling all thecore space not occupied by the conductors. Each of the insulatedconductors 17 and 21 comprises a group of metallic, stranded wires 18surrounded by a tightly fitted, tubular sheath of insulating material19. Insulating material 19 is preferably an extrudable plastic whichaffords a high quality of electrical insulation for a relatively thinsection and which has a relatively low dielectric constant. Forextremely high temperature applications, a preferred insulating material19 may be, for example, a suitable one of the group of fluorinatedethylene propylene plastics manufactured by -E. I. du Pont de Nemours &Co., Inc., and sold under the trademark Teflon, and, more particularly,Teflon lOO-X PEP-fluorocarbon resin. This material has a maximumrecommended operating temperature of 400 Fahrenheit but will operatesatisfactorily at much higher temperatures for the short periods of timerequired in well logging use. For lower temperature applications, theremay be employed a suitable one of the polypropylene plastics, as, forexample, the product manufactured by Enjay Co., Inc., a division ofHumble Oil & Refining Co., and sold under the trademark Escort or theproduct manufactured by Hercules Powder Co., and sold under thetrademark Pro-fax. These materials have maximum recommended operatingtemperatures in excess of 300 Fahrenheit.

Each of the above-described materials has a dielectric constant ofapproximately 2, whereas the insulating materials usable with thepresent form of construction have dielectric constants of approximately5. Thus, the capacitance to ground of the conductors is substantiallyreduced. Moreover, the above materials provide much better electricalinsulation even though a thinner wall section is utilized. For example,a cable constructed in accordance with the invention and utilizing asheath of the above-described Teflon with a wall thickness of .008"exhibited an insulation resistance to 500 volts DC. of approximatelyohms/1000 when placed in water at 350 Fahrenheit, whereas a cableconstructed in accordance with the present state of the art andutilizing a synthetic rubber sheath with a .030" wall thicknessexhibited insulation resistance of about 10 ohms/1000' under the sametest conditions.

The matrix 15, as clearly shown in FIG. 2, is a monolithic mass ofmaterial which encases all the insulated conductors, fills all the corespace not occupied by the conductors, and defines the outer surface ofthe core. However, in FIG. 1, for purposes of illustration anddescription, matrix has been broken away to show an outer matrix section16 and an inner matrix section 20. Inner matrix sections surroundscentral conductor 21 and maintains the outer conductors 17 inspaced-apart relationship and away from central conductor 21. Outermatrix section 16 covers the outer conductors 17 and is of sufficientthickness toprotect the insulating material 19 from physical abuse .ordamage. It is emphasized that sections 16 and 20 are not separatestructural elements, at least in the finished core, and the terms aremerely descriptive of portions of a monolithic mass of semiconductivematerial which encases the insulated conductors 17 and 21.

1 To provide electrical shielding for reducing the effects of capacitivecoupling between conductors, the material used for matrix 15 iselectrically semiconductive. Thus, each of the conductors 17 and 21 issurrounded by portions of a monolithic, semiconductive mass of materialwhich has its outer surface in direct contact with the grounded innerlayer of armor strands 21. The arrangement of outer conductors 17 in aspaced-apart relationship and away from central conductor 21 provides anelectrical path of relatively large cross-sectional area from any pointwithin matrix 15 to the grounded armor strands 12. Even though matrix 15may have a higher volume resistivity than the conductive films utilizedin the prior art cables, the greater cross-sectional area of theelectrical paths plus the absence of breaks and discontinuities withinthe shielding material, as provided by the invention, results in lowerelectrical resistances to ground, particularly from points within theinterior portions of the matrix.

The material for matrixlS is preferably an extrudable, semiconductive,oil and-gas-resistant elastomer which cures to a hard, flexible,relatively incompressible form and maintains its physical properties atborehole temperatures and pressures. For example, various compounds ofthe acrylonitrile-butadiene rubbers, such as the product manufactured byB. F. Goodrich Chemical Co. and sold under the trademark Hyoar, may beemployed. As a further example, there may be utilized various compoundsof thepolychloroprene rubbers (commonly known as neop-renes); and, inparticular, a compound utilizing a non-sulphur modified general purposeneoprene, such as type W, has been employed.

The products described above for use as insulating material 19 and asmaterial for matrix 15 and other products having similar properties arewell known to the art and the materials as such form no part of thepresent invention. However, the use of such materials is permitted onlyby the novel and useful form of construction provided by the invention.For example, the previously described Teflon material, which is known tobe a superior electrical insulator and to have a low dielectricconstant, could not be satisfactorily substituted for the insulatingmaterials used in present well logging cables since, for example, itsphysical properties are not adequate to resist the pressure exerted bythe armor strands and there is no practical method of applying ashielding film to its outer surface.

Referring now to FIG. 3, there is illustrated schematically apparatusfor fabricating, in accordance with the method aspect of the invention,a well logging cable of the type shown in FIGS. 1 and 2. The insulatingmaterial 19 is extruded about the individual stranded wires 18 (shown inFIGS. 1 and 2) in a conventional manner (apparatus not shown) and theinsulated conductors 17 and 21 are then wound upon reels 31 and 29,respectively. The central insulated conductor 21 is processed from reel29 through a conventional extruding machine 30 where the uncured innermatrix section 20 is extruded about it. Reels 31, upon which are woundouter conductors 17, are mounted upon a conventional winding machine(not shown) which may be rotated about the path of central conductor 21;and conductors 17 are threaded through a winding die 32 which guidesthem into spaced-apart positions about inner matrix section 20 as thewinding machine is rotated. During the winding operation, conductors 17are kept under sufficient tension to partially embed them in the surfaceof uncured inner matrix section 20. Thus, portions of inner matrixsection 20 will protrude between adjacent ones of outer conductors 17.From winding die 32 the assembly passes to a second conventionalextruding machine 33 where the uncured outer matrix section 16 isextruded about it. A long hand die is preferably used in extrudingmachine 33 so :as to fill throughly the interstices between outerconductors 17 and thereby form a union between outer matrix section 16and the portions of inner matrix section 20 protruding between adjacentones of the outer conductors. The assembled core is then passed througha conventional curing oven 34 to cure the matrix material and thefinished core 14 may be spooled upon reel 35. Alternative known methodsof curing, as, for example, pan curing or curing by means of chemicalaccelerators, may of course be utilized. After curing, core 14 may bedrawn through a conventional armoring machine (not illustrated) whichperforms armor strands 11 and 13 and winds them in concentric layers 10and 12 about the core, as shown in FIGS. 1 and 2.

Since the final layer of the core is applied by extrusion, its diametermay be controlled with great accuracy, thus permitting better control ofthe coverage of the inner layer of armor strands.

A further improvement in armor coverage may be effected by winding atleast the inner layer of armor strands 12 before the core is completelycured and winding them under'sufiicient tension to partially embed themin the surface of the matrix. After curing, the outer surface of core 14will be permanently ridged to fit the interstices between the innerarmor strands 13. Thus, the core will not tend to undergo furtherpennanent deformation when the cable is placed under tension at hightemperatures and the diameters of the armor strand layers and 12 willtend to remain more constant.

While a specific well logging cable has been disclosed herein forpurposes of explanation, it should be apparent that cables incorporatingdifferent conductor arrangements and comprising more or less than sevenconductors may be constructed without departing from the scope of theinvention in its broader aspects. Accordingly, the invention is not tobe limited except as defined in the appended claims.

What is claimed is:

1. In a method of manufacturing an armored, loadbearing, multiconductor,electrical cable, the steps of: extruding an elongated inner matrixsection of generally circular cross section; arranging a plurality ofelongated, insulated, electrical conductors in spaced-apart relationshipabout the outer surface of said elongated inner matrix section andcoextending longitudinally of said section while maintaining sufficienttension on said insulated conductors to partially embed them in saidsurface; extruding an outer matrix section of generally cylindricalouter periphery about said arranged insulated conductors and innermatrix section to form, together with said inner matrix section, amatrix completely encasing said insulated conductors, said inner andouter matrix sections comprising an uncured, semiconductive elastomer;and curing said elastomer to form a monolithic matrix.

2. In a method of manufacturing an armored, loadbearing, multiconductor,electrical cable the steps of: extruding an inner matrix sectioncomprising an uncured, semiconductive elastomer concentrically about aninsulated electrical conductor; arranging a plurality of insulatedelectrical conductors in spaced-apart relationship about said innermatrix section while maintaining sufficient force on said plurality ofinsulated conductors to partially embed them in the surface of saidinner matrix section; extruding an outer matrix section comprising saidelastomer about said assembled conductors and inner matrix section; andcuring said elastomer.

3. The method of manufacturing a load-bearing, multiconductor,electrical cable comprising the steps of: extruding separate sheaths ofplastic insulating material concentrically about each of a plurality ofelongated electrical conductors; extruding a cylindrical inner matrixsection comprising an uncured, semiconductive elastomer; arranging saidinsulated conductors helically in spaced-apart relationship about saidinner matrix section while maintaining force on said insulatedconductors to partially embed said conductors in the surface theeof;extruding an outer matrix section comprising said uncured,semiconductive elastomer about said inner matrix section and arrangedinsulated conductors to form, together with said inner matrix'section, amatrix of generally cylindrical, smooth outer periphery which completelyencases said insulated conductors; curing said elastomer to form amonolithic matrix; winding a first layer of load-bearing armor strandshelically about the outer surface of said matrix; and winding a secondlayer of load-bearing armor strands-helically about said first layer andin the opposite direction.

4. The method of manufacturing a load-bearing, multiconductor,electrical cable comprising the steps of: extruding a tubular sheath ofplastic insulating material concentrically about each of a plurality ofelongated, metallic,

electrical conductors; extruding an inner matrix section of a generallycircular cross section comprising an uncured, semiconductive elastomerconcentrically about one of said insulated conductors; winding saidother insulated conductors helically in spaced-apart relationship aboutthe outer surface of said inner matrix section while said elastomer isat least partially uncured and while maintaining sufiicient tension onsaid insulated conductors to partially embed them in said surface;extruding an outer matrix section comprising said uncured,semiconductive elastomer about said wound insulated conductors and innermatrix section to form, together with said inner matrix section, amatrix of generally cylindrical outer periphery which completey encasessaid insulated conductors; curing said elastomer to form a monolithic matrix; winding a first layer of metallic armor strands helical- 'ly inone direction and in side-by-side relationship about the outer surfaceof said matrix and substantially covering said matrix; and Winding asecond layer of metallic armor strands helically in the directionopposite to said one direction and in side-by-side relationship aboutsaid first layer and substantially covering said firstlayer.

5. The method of manufacturing a load-bearing, multi- I conductor,electrical cable comprising the steps of: extruding an elastomer to forma cylindrical inner matrix section; arranging insulated conductorshelically in spacedapart relationship about the outer cylindricalsurface of said inner matrix section While maintaining suflicienttension on said insulated conductors to partially embed them in saidsurface; extruding an elastomer outer matrix section about said innermatrix section and arranged insulated conductors to form, together withsaid inner matrix section, a matrix having a generally cylindrical,outer pe riphery and which matrix completely encases said insulatedconductors; and winding a layer of load-bearing armor strands helicallyabout the outer surface of said matrix under sufiicient tension topartially embed said armor strands in the outer periphery of saidmatrix;

6. The method of manufacturing a load-bearing, mu-lti conductor,electrical cable comprising the steps of: extruding a cylindrical innermatrix section of uncured elastomer; arranging insulated conductorshelically in spaced-apart relationship about the outer cylindricalsurface of said inner matrix section While maintaining suflicienttension on said insulated conductors to partially embed them in saidsurface; extruding an outer matrix section of said uncured elastomerabout said inner matrrx section and arranged insulated conductors toform, when cured together with said inner matrix section, a monolithicmatrix having a generally cylindrical, outer periphery and whichmonolithic matrix completely encases said insulated conductors; windinga layer of loadbeanng armor strands helically about the outer surface ofsaid matrix under sufiioient tension to partially embed sa d armorstrands in the outer periphery of said matr x; and curing said elastomerto form a monolithic matr1x having its outer surface permanently ridgedin the interstices between said armor strands.

7. In a method of manufacturing an armored, loadbearmg, multieonductor,electrical cable, the steps of: arranging a plurality of elongated,insulated, electrical conductors in spaced-apart relationship about anelongated, generally cylindrical inner matrix section and coextendlnglongitudinally of said section while maintaining sufiicient force onsaid plurality of conductors to partially embed them therein, saidpartially embedded con ductors partially extending beyond the outerperiphery of said inner matrix and said inner matrix partially fillingthe interstices between said conductors; extruding an outer matrixsection onto and about said arranged insulated conductors and innermatrix section to form, together with said inner matrix section, amatrix completely encasing said insulated conductors, said inner andouter matrix sections comprising an uncured, semiconductive elastomer;and curing said elastomer to form a monolithic matrix.

8. In a method of manufacturing an armored, loadbearing, multiconductor,electrical cable, the steps of: applying forces to a plurality ofelongated, insulated, electrical conductors to partially embed saidconductors in spaced-apart relationship in the outer surface of anelongated, generally cylindrical inner matrix section and coextendinglongitudinally of said section, said section comprising a smooth,uncured, semiconductive elastomer; extruding an uncured elastomer oversuch partially embedded conductors and inner matrix section to form anouter matrix section which together with said inner matrix sectioncompletely encases said insulated conductors into a completely solidmass; and curing said inner and outer matrix sections to form a hard,monolithic matrix in which said insulated conductors are embedded.

References Cited by the Examiner UNITED STATES PATENTS 1,977,209 10/1934Sargent 264174 1,982,288 11/1934 Evans 264-103 X 2,199,526 5/1940McCowen 264171 X 2,544,503 3/1951 Kennedy 156-56 X 2,810,424 10/ 1957Swartswelter et a1. 264103 FOREIGN PATENTS 205,315 12/ 1956 Australia.526,895 9/ 1940 Great Britain.

ROBERT F. WHITE, Primary Examiner.

M. R. DOWLING, Assistant Examiner.

1. IN A METHOD OF MANUFACTURING AN ARMORED, LOADBEARING, MULTICONDUCTOR,ELECTRICAL CABLE, THE STEPS OF: EXTRUDING AN ELONGATED INNER MATRIXSECTION OF GENERALLY CIRCULAR CROSS SECTION; ARRANGING A PLURALITY OFELONGATED, INSULATED, ELECTRICAL CONDUCTORS IN SPACED-APART RELATIONSHIPABOUT THE OUTER SURFACE OF SAID ELONGATED INNER MATRIX SECTION ANDCOEXTENDING LONGITUDINALLY OF SAID SECTION WHILE MAINTAINING SUFFICIENTTENSION ON SAID INSULATED CONDUCTORS TO PARTIALLY EMBED THEM IN SAIDWURFACE; EXTRUDING AN OUTER MATRIX SECTION OF GENERALLY CYLINDRICALOUTER PERIPHERY ABOUT SAID ARRANGED INSULATED CONDUCTORS AND INNERMATRIX SECTION TO FORM, TOGETHER WITH SAID INNER MATRIX SECTION, AMATRIX COMPLETELY ENXASING SAID INSULATED CONDUCTORS, SAID INNER ANDOUTER MATRIX SECTIONS COMPRISING AN UNCURED, SEMICONDUCTIVE ELASTOMER;AND CURING SAID ELASTOMER TO FORM A MONOLITHIC MATRIX.